Active implantable medical devices have a housing generally designated as the “generator,” that is mechanically and electrically connected to one or more “leads” having electrodes that contact the patient's tissue at one or more locations where it is desirable to apply stimulation pulses and/or to collect (detect) an electrical signal: e.g., myocardium, nerve, muscle, or other organ tissue.
Standardized connection systems have been developed to ensure interchangeability of leads and generators that are produced by different manufacturers. Thus, the standard called “IS-1” and “IS-4” define a number of dimensional and electrical characteristics for the leads used for cardiac pacing (i.e., the delivery of low energy level stimulation pulses to cause a heartbeat). For defibrillation or cardioversion leads, wherein higher energy “shock” stimulation pulses pass from the generator to the lead, and the electrical stresses are more severe, the standards called “DF-1” and “DF-4” define the dimensional and electrical characteristics of the lead-generator connection system.
The complexity of these leads, which already incorporate specific constraints in terms of electrical energy associated with either use, pacing or shock, is enhanced by the development of multisite devices and intracardiac biological sensors such as peak endocardial acceleration (PEA) sensors. This results in terms of connectivity, in a proliferation of connection plugs, in addition to different standards depending on the plugs.
The benefit of a single plug, subject to a single standard, with a plurality of electrical contacts to simultaneously ensure connections to various terminals of the generator for all energy levels is understandable, whether for the collection of depolarization signals, for the application of low energy stimulation pulses for pacing, or the delivery of a high energy defibrillation shock.
In this context, a single “isodiametric” connection plug, that is to say a plug with a uniform cylindrical shape, designed to be inserted in a counterpart cavity of the generator, is disclosed.
EP 1641084 A1 and its US counterpart U.S. Pat. No. 7,175,478 (both assigned to Sorin CRM S.A.S. previously known as ELA Medical) describes such an isodiametric connection plug with the outer cylindrical surface having a stack of annular electrical contact zones, constructed with conductive cylindrical rings and insulating zones designed to electrically isolate the conductive rings.
For receiving a multipolar connection plug of this type and for connecting it to the electrical circuits of the generator, connectors comprising a cavity formed similarly to the plug itself are provided. The connector cavity thus also comprises a stack of annular electrical contacts to ensure electrical contact with the corresponding conductive rings of the connection plug. In this stack, the annular elements for electrical contact are separated by isolation annular elements.
It should be understood that, unlike the IS1/DF1 connection plug standard, wherein the isolation elements are carried by the lead, under the newer IS4/DF4 standard, the isolation elements are now arranged in the cavity, which has the advantage of providing new isolation elements each time the generator is replaced.
The term “isolation” used here applies both to the sealing of the cavity relatively to the external environment, especially with respect to body fluids, and to the electrical insulation, that is to say the low voltage and high voltage insulation of the electrical contact elements of the cavity, as well as the electrical contact elements of the cavity with the outside environment.
U.S. Pat. Publication No. 2005/0186829 A1 describes a connector comprising a series of stackable pieces that snap together with alternatively the insertion of a flexible joint or of an electrical connection element. Each flexible joint, or connection element, is thus pinched between two of these counterpart pieces. The tightness of this connector is nevertheless not satisfactorily ensured at the interface between the two snap-together pieces, which leaves a risk of infiltration from the environment inside the connector, particularly at the electrical connection members. It is therefore necessary to provide an additional sealing level, for example, by gluing the snap pieces, by force-fitting such as a “press-fit,” or by other similar means.
U.S. Pat. No. 7,083,474 B1 also proposes a flexible joint overmolded onto a stiffening core carrying crossing holes. The rigid core carries an abutment during stacking of the various elements of the cavity. However, because the seal is not anchored, but simply attached to the rigid core through the crossing holes, nothing prevents it from moving during the insertion of the connector plug, which may degrade the sealing and electrical insulation.
U.S. Pat. Publication No. 2003/0073348 A1 describes yet another connector, made from a stack of support elements alternately attaching seals and electrical connection elements. But the drawbacks described above (imperfect seal and necessary use of an additional level of sealing, for example, by gluing or “press-fit”) still remain.